Materials Science
Unconventional magnetoelastic behavior in Al rich CoFeAl Films with inverse Heusler like local order for flexible spintronics
Rupalipriyadarsini Chhatoi, Anuroopa Behatha, Swayang Priya Mahanta et al. (+6 more)
Strain engineering of
magnetic properties offers a promising route toward flexible spintronic applications. Here, we report an unconventional magnetoelastic response in Al rich Co Fe Al thin films on flexible substrates using strain dependent magneto optical Kerr effect microscopy and magnetometry measurements. While the films exhibit a conventional positive magnetostriction coefficient, consistent with standard in plane easy axis rotation under stress, their saturation magnetization increases under compressive strain and decreases under tensile strain. First principles calculations reveal that this unconventional response originates from a strain induced competition between exchange splitting and
crystal field effects in an inverse Heusler like local environment created by Al enrichment. This leads to a highly sensitive, sublattice dependent
magnetic state, consistent with a strain induced reconfiguration of Co and Fe moments. Our results demonstrate that local compositional tuning can fundamentally alter magnetoelastic behavior, establishing strain controlled sublattice compensation as a route toward programmable
magnetic functionality in flexible spintronic systems.
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All authors Rupalipriyadarsini Chhatoi, Anuroopa Behatha, Swayang Priya Mahanta, Shubhransu Sahoo, Soubhagya Dash, Bhuvneshwari Sharma, Abhisek Mishra Esita Pandey, Satadeep Bhattacharjee, Subhankar Bedanta
Cosmology and Nongalactic Astrophysics
Evolving dark energy and a younger Universe from cosmic inhomogeneity
Jacky David Yang and Hans-Otto Carmesin
Joint analyses of
baryon acoustic oscillations, type Ia
supernovae and the
cosmic microwave background show a preference for an evolving dark-energy equation of state, and recent studies suggest that
cosmic inhomogeneities can produce an apparent
evolution of dark energy within general relativity. Here we examine this effect within a framework in which the possibility that matter can be unevenly distributed enters the expansion dynamics directly. The framework yields
redshift-dependent effective values of the Hubble constant and of the dark-energy density parameter without introducing a new free parameter. Using CMB-inferred parameters to fix the homogeneous limit, we find that the dark-energy density parameter increases by about eight percent toward the present, from 0.679 to 0.735, while the inferred Hubble constant shifts from the Planck value toward the range obtained from local measurements. Both trends are broadly consistent with published estimates from
supernovae,
baryon acoustic oscillations, X-ray clusters and gravitational waves, although a joint analysis of the underlying data is left for future work. Integrating the resulting expansion history gives a present-day
cosmic age of 13.521 Gyr, compared with 13.827 Gyr for the homogeneous model; we interpret the difference of 0.306 Gyr as a global time dilation between the two descriptions. The framework also yields the homogeneous-limit dark-energy density parameter, two thirds, from the formation of volume alone. The predicted
redshift dependences can be tested against forthcoming measurements of
cosmic distances and expansion rates.
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Quantum Physics
Sipser-Spielman meets Dijkgraaf-Witten: non-Abelian qLDPC codes via twisted sheaf gauge theory and almost-constant-overhead magic state fountain
Guanyu Zhu, Shi Jie Samuel Tan, Ryohei Kobayashi et al. (+1 more)
Sipser-Spielman codes and Dijkgraaf-Witten twisted gauge theories are among the most profound ideas in the last few decades in the areas of computer science and mathematical physics respectively. This work unifies them in the same framework using the
language of sheaf
cohomology, and produces a new framework of twisted sheaf gauge theories describing a class of
quantum low-density parity-check (qLDPC) codes with non-Abelian $D_4$ topological order. The corresponding twisted Clifford-stabilizer qLDPC code can be obtained from gauging a new type of 0-form sub-complex
symmetry from a qLDPC code defined on a general sheaf complex, and can be interpreted as a topological defect network of non-Abelian $D_4$ patches glued together with proper gapped interfaces. As an application, one can use this to realize a magic state fountain via the gauging measurement of the addressable logical CZ gates as 0-form subcomplex
symmetries in a 2D hypergraph-product (HGP) sheaf code. This includes a scheme of subdividing an arbitrary constant-rate 2D HGP code with parameters $[[n,\Theta(n), \Omega(n^{1/2})]]$ into a
quantum sheaf code which allows preparation of $\Theta(n^{1/2})$ logical CZ magic states in parallel, equivalent to the recent
geometric construction using the code-to-
manifold mapping in (arXiv:2601.06736). Moreover, using the recent sheaf complex and algebraic code constructions by Golowich-Tamo-Zhu (arXiv:2609.27801) with parameters $[[n,\Theta(n^{1-\epsilon}), \Omega(n^{(1-\epsilon)/2})]]$ for arbitrary small $\epsilon$, one can prepare $\Theta(n^{1-\epsilon})$ CZ magic states in parallel and hence achieve an almost-constant magic rate.
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All authors Guanyu Zhu, Shi Jie Samuel Tan, Ryohei Kobayashi, Po-Shen Hsin
Physics and Society
Collective impact of opinion formation on agent-based epidemic dynamics
Andrea Bondesan, Riccardo Vecchio, Chiara Barbati et al. (+3 more)
Epidemic spread and collective opinion formation are tightly coupled processes: individual beliefs about the severity of an outbreak and the value of protective measures shape behavior, while the evolving epidemic itself reshapes public sentiment through risk perception. We propose an
agent-based framework that couples opinion dynamics with a compartmental epidemic model, in which each
agent carries both a health status and a continuous opinion variable describing adherence to protective measures. Opinion
evolution is driven by binary interactions among
agents and by an exogenous background field that reflects the current state of the epidemic, while the disease transmission rate depends explicitly on the opinions of interacting
agents. Using methods of statistical mechanics, we characterize the resulting macroscopic system for the compartmental mass fractions and mean opinions in both far-from-
equilibrium and close-to-
equilibrium regimes. The calibration shows that incorporating behavioral opinion dynamics substantially improves the interpretation of epidemic
evolution. In particular, the inferred risk perception function evolves consistently with the observed epidemic burden, indicating that behavioral adaptation can explain part of the temporal variation that would otherwise be absorbed into time-dependent transmission parameters. Our results illustrate how integrating opinion heterogeneity in kinetic epidemic models offers quantitative insights into the feedback between behavior and disease spread.
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All authors Andrea Bondesan, Riccardo Vecchio, Chiara Barbati, Jonathan Franceschi, Anna Odone, Mattia Zanella
Accelerator Physics
Generation of 10-TW Attosecond X-Ray Pulses in a Free Electron Laser
E.A.Schneidmiller, S.Serkez, I.Zagorodnov et al. (+35 more)
Attosecond pulses provide direct access to electron dynamics in atoms, molecules, and solids on their natural timescales. While table-top sources have achieved attosecond pulse durations at moderate intensities, extending attosecond science to high peak powers in the x-ray regime requires free-electron
lasers (FELs). Here we report the generation of soft-x-ray pulses with a duration of $\sim\!100$ as and peak power on the order of 10 TW at the European XFEL. The unprecedented combination of pulse duration and peak power is enabled by operation of a soft-x-ray undulator at high electron energy together with five-stage bunch compression, producing ultrahigh peak currents. These millijoule-level attosecond x-ray pulses establish a new regime for attosecond science.
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All authors E.A.Schneidmiller, S.Serkez, I.Zagorodnov, N.Gerasimova, M.Scholz, N.Golubeva, M.Guetg, G.Geloni, S.Karabekyan, F.Sottocorona, A.Trebushinin, G.Perosa, S.Tomin, F.Mayet, Th.Maltezopoulos, J.Gruenert, J.Laksman, H.Ahmadi Rashtabadi, T.M.Baumann, R.Boll, F.Calegari, G.Catacchio, S.Dold, D.E.Ferreira de Lima, L.Funke, W.Helml, M.Ilchen, T.Mazza, M.Meyer, T.Mullins, M.Robinson, S.Savio, K.Scharei, Ph.Schmidt, A.Thiel, S.Usenko, L.Wuelfing, W.Decking
Materials Science
Structural prediction of B$_{18}$Y$_{2}$ cluster: A Machine-Learning-Assisted Basin-Hopping Study
Peter Ludwig Rodríguez-Kessler
The structural and optical properties of the doubly yttrium-doped boron cluster B$_{18}$Y$_2$ have been systematically investigated using density functional theory calculations. The lowest-energy structure was identified through extensive basin-hopping searches accelerated by a pre-trained MACE machine-learning potential and subsequently refined and validated at the DFT level. The resulting global-minimum structure adopts a double-ring geometry, consisting of two fused B$_9$ rings stabilized by yttrium atoms positioned above and below the boron framework. Vibrational frequency calculations confirm the dynamical stability of the optimized structure, while the calculated infrared and UV–Vis spectra provide characteristic signatures of the Y–B interactions and the electronic structure of the boron framework. These results demonstrate how yttrium doping can stabilize unusual double-ring boron architectures and highlight the effectiveness of machine-learning-assisted basin-hopping searches for exploring the complex potential-energy landscapes of doped boron clusters.
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General Relativity and Quantum Cosmology
Spectral Invariance for Black-Hole Differential Observables
Vedant Subhash
We study first-order differential quantities built from solutions of second-order black-hole wave equations. These quantities can satisfy new differential equations that contain extra singular points, even when the original physical solutions remain regular. We show that an isolated zero of the transformation determinant can produce such an apparent singularity, but it does not by itself create a new resonance or quasinormal-mode frequency. We then study the corresponding Green functions and show that the physical transformed response has the same spectral poles as the original problem, provided that the transformation does not become globally degenerate. For the Regge–Wheeler and Zerilli equations, this means that ordinary turning points can appear as singular points of the derivative equation without changing the nonzero-frequency quasinormal-mode spectrum. The zero-frequency case is different and must be studied separately.
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Quantum Physics
Quantum-HPC Workflows Across Multiple Quantum Computing Platforms: Two Case Studies
Philipp Seitz, Miwako Tsuji, John Children et al. (+5 more)
We describe the
Quantum-HPC hybrid system comprising the supercomputer Fugaku, the QPUs Quantinuum Reimei and ibm_kobe, and the Tierkreis hybrid workflow software. We present two demonstrations of the system at work. In the first, we compute the excited states of a biomolecular system using Fugaku and Reimei (simulator) to handle classical and
quantum parts of the workflow respectively. In the second, Fugaku coordinates Reimei and ibm_kobe working together in a combined VQE + QPE workflow to compute the ground state energy of a simple system.
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All authors Philipp Seitz, Miwako Tsuji, John Children, Yuta Kikuchi, Riku Masui, Juan Pedersen, Kentaro Yamamoto, Ross Duncan
Accelerator Physics
Fabry-Pérot Resonance Shifts as a Novel Non-destructive In Situ Surface Damage Diagnostic
Gregory Blume, Colin Kirk, Sushil Poudel et al. (+6 more)
Current surface damage evaluation for nanostructured electronic devices requires specialized equipment or conditions outside the designed operating environment and cannot be used for in situ evaluation of surface damage. In this work, we developed a non-destructive method to probe the surface sublimation of a
semiconductor heterostructure which can be applied to other
semiconductor damage mechanisms. This approach employs shifts in the resonances of an optical cavity comprising the surface and an integrated distributed Bragg reflector fabricated below the
semiconductor heterostructure undergoing sublimation. We performed the demonstration of this technique under
vacuum, but surface damage effects can be observed in any operational environment either in situ or ex situ.
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All authors Gregory Blume, Colin Kirk, Sushil Poudel, John Hill, Alimohammed Kachwala, Joseph Grames, Marcy L. Stutzman, Matt Grau, Sylvain Marsillac
Statistical Mechanics
Complexity drives the symmetry breaking of temperature fluctuations
D. Rosales Herrera, M. Y. Gallegos Ruiz, A. Fernández Téllez et al. (+2 more)
Frequently, nonextensive systems are described through $q$-exponential functions, where the $q$-parameter determines how far a system is from
equilibrium. In this work, we study systems constrained to $q-1\ll1$ to describe systems near thermal
equilibrium, and derive the probability density function and temperature fluctuations. To this end, we derive the series expansion of the $q$-exponential function, yielding a perturbative series that is a superposition of gamma distributions. On the other hand, the temperature fluctuations are expressed as a superposition of Dirac delta functions and their derivatives, meaning that the bulk of the system remains at a constant temperature, while point-temperature variations emerge, marking the system's departure from thermal
equilibrium. The statistics of the temperature fluctuations exhibit a transition from a symmetric to a nonsymmetric distribution as the nonextensive parameter increases. These results provide evidence of the association between the emergence of nonextensivity and the
symmetry breaking of temperature fluctuations.
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All authors D. Rosales Herrera, M. Y. Gallegos Ruiz, A. Fernández Téllez, J. R. Alvarado García, J. E. Ramírez
Quantum Physics
Complexity Barriers to State Preparation in Quantum Approximate Optimization
Stuart Hadfield
For many important optimization problems we are restricted to approximate solutions in practice due to computational complexity. Distinct from the exact optimization setting, approximate optimization admits performance measures beyond whether the optimum is found, with different tradeoffs and complexity. For MaxCut, a near-unity (ordinary) approximation ratio can coexist with near-zero improvement (gain) over a random cut. For the standard encoding, the unconditional classical MaxCut-Gain hardness gap implies that any uniformly efficient
quantum or hybrid procedure recovering a fixed positive fraction of the optimal classical gain on every input, with at least inverse-
polynomial success probability, would place NP in BQP. Such a procedure is therefore believed impossible under standard assumptions. We broadly address where our worst-case barriers do or do not apply across the
quantum algorithm landscape. We prove that the barrier survives
quantum random access optimization (QRAO) compression and applies between the classical and relaxed optimal values. For every input, a product state attains the classical optimum. Thus the barrier to reaching the classical threshold does not arise from a need for
entanglement. For $d\in\{2,3\}$ variables per
qubit, the known decoder transfers encoded energy gain to decoded mean gain by the exact factor $1/d^2$. Combining this identity with MaxCut-Gain hardness gives an operational preparation barrier for QRAO. We also construct hard $n$-
qubit families with relative
quantum relaxation excess $\Theta(1/n)$, while the maximally mixed state has energy approximation ratio $1-\Theta(1/n)$, zero encoded energy gain, and hence zero decoded mean gain. Our results separate the effects of relaxation tightness and energy approximation from operational accessibility, motivating more comprehensive accounting in benchmarking and performance assessment.
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Materials Science
Retrainable physics-integrated neural differentiable modeling of sintering across material systems
Zeping Chen, Ani Aprahamian, Khachatur V. Manukyan et al. (+1 more)
Sintering is widely used to manufacture ceramics, but coupled densification and grain growth, material-dependent kinetics, and sparse measurements complicate predictive modeling and process design. We present Sinter-PiNDiff, a retrainable physics-integrated neural differentiable framework for predicting density and grain-size
evolution. Two neural networks learn densification and grain-growth coefficients within coupled rate equations, while a smooth saturation factor attenuates densification near theoretical density. The same governing structure, network architecture, and training procedure were fitted independently to published data for MgO, Al-doped ZnO, and CaO-doped ThO2. Tests at held-out temperatures and compositions yielded the lowest mean error in all twelve material-metric comparisons against multilayer perceptron and residual network baselines. For MgO, Al-doped ZnO, and CaO-doped ThO2, respectively, density normalized root-mean-square errors were 14.6%, 10.8%, and 14.4%, and grain-size errors using the same metric were 8.6%, 12.1%, and 19.3%. Removing evolving density from both neural-network inputs increased density and grain-size trajectory errors in all three systems and ten of twelve aggregate errors, supporting density-dependent kinetic feedback. Deep ensembles estimated model disagreement, but empirical coverage showed that the uncertainty bands were not calibrated and did not capture all model-data discrepancies. These results establish Sinter-PiNDiff as a retrainable framework for sparse-data prediction and uncertainty-informed selection of sintering conditions.
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All authors Zeping Chen, Ani Aprahamian, Khachatur V. Manukyan, Tengfei Luo
Solar and Stellar Astrophysics
The 91T/99aa-like Type Ia Supernova 2019vrq, Part I: Photometry, Spectroscopy, and Spectropolarimetry of a Nearly Standard Candle
Yi Yang, Peter Hoeflich, J. Craig Wheeler et al. (+16 more)
Among the various major subtypes of Type Ia
supernovae (SNe), the luminous 1991T-like (Filippenko et al. 1992; Phillips et al. 1992) and 1999aa-like (Krisciunas et al. 2000; Garavini et al. 2004) events stand out as particularly important for constraining the explosion mechanism. Their white
dwarf (WD) progenitors are thought to have masses close to or exceeding the Chandrasekhar limit. We present spectrophotometric and polarimetric time-series observations of the overluminous Type Ia SN2019vrq. Between -9 and +12 days relative to the light-curve peak, its continuum polarization is consistent with zero, as seen in most normal-bright SNeIa and despite a possible rise up to 0.2% toward longer wavelengths as seen in subluminous SNeIa. Polarization across major spectral features is marginal ($\lesssim$0.3%) with the exception of the high-velocity CaII near-infrared triplet, which reaches $\sim$0.5%. This low polarization indicates a substantially spherically symmetric electron-scattering photosphere and minimal large-scale ejecta asymmetry. Early-time spectra reveal hot, doubly ionized ejecta dominated by SiIII and blended iron-group features. Intermediate-mass-element lines, such as CaII and SiII, are more clearly seen than in 91T-like events, though these lines remain weaker than in normal SNeIa. The intrinsically higher peak luminosity of overluminous 91T/99aa-like SNeIa (Yang et al. 2022; Phillips et al. 2024), their comparatively short formation timescale for a massive WD progenitor - a channel that becomes more common toward high
redshift, and the moderate viewing-angle dependence of their spectrophotometric properties as inferred from their persistently low polarization, together suggest that this subclass may serve as a promising standard candle at high
redshift.
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All authors Yi Yang, Peter Hoeflich, J. Craig Wheeler, Dietrich Baade, Lifan Wang, Aleksandar Cikota, D. Andrew Howell, Curtis McCully, Alexei V. Filippenko, Ferdinando Patat, Chris Ashall, Mattia Bulla, Avishay Gal-Yam, Melissa. L. Graham, Daichi Hiramatsu, Divya Mishra, Estefania Padilla Gonzalez, Craig M. Pellegrino, Steve Schulze
High Energy Physics (Theory)
Bound States in 2d Yukawa Theory from Hamiltonian Truncation
Olivier Delouche, Kara Farnsworth and Francesco Riva
We study the spectrum of two-dimensional Yukawa theory using
Hamiltonian truncation, with a focus on bound states. We extend the framework of
Hamiltonian truncation effective theory to include
fermions and logarithmic UV divergences. With these corrections, the energy levels converge as a function of the cutoff with the scaling predicted by power counting. We identify a strategy to follow the
evolution of
fermion-antifermion bound states from weak to strong coupling, and investigate its binding energy, finding good agreement with finite-volume perturbation theory at weak coupling. Finally, we explore the heavy-scalar regime toward the massive Thirring/Sine-Gordon limit, recovering the expected weak-coupling behavior and outlining how the calculation can be extended toward this limit.
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Solar and Stellar Astrophysics
Physics-induced impact on the properties of Kepler/K2 solar analogs in the light of PLATO's requirements
Saniya Khan, Gaël Buldgen, Jérôme Bétrisey et al. (+2 more)
Solar analogs are useful laboratories for tests of
stellar structure and
evolution, particularly in the context of the upcoming PLATO mission. Our study focuses on six seismic
solar analogs observed by Kepler and K2. We investigate the impact of the model physical ingredients on these six targets in order to evaluate how well one can satisfy the PLATO precision requirements for
stellar parameters with the data quality that is currently available to us. We used as reference values the
stellar mass, age, and chemical composition obtained with the Forward and Inverse COmbination (FICO) procedure, based on OPAL opacities and a combination of NACRE II and
Solar Fusion II (SFII)
nuclear reaction rates. The efficiency of macroscopic transport is calibrated on lithium abundances derived from the analysis of HERMES spectra. From there, we carried out extensive tests of the physical ingredients with the help of a Levenberg-Marquardt local minimisation method using both classical and seismic constraints. In particular, we investigated the impact induced by the use of OPLIB opacities and SFIII
nuclear reaction rates on the
stellar fundamental properties, as well as the use of various seismic constraints. We quantify the potential differences that changes in the modelling input physics may lead to, and compare their extent with the requirements expected for the PLATO mission (15% in mass, 2% in radius, and 10% in age), providing crucial constraints on the accuracy and robustness with respect to systematics of the determination of fundamental properties for PLATO. For our sample of
solar analogs, we are able to accurately retrieve
stellar masses within 2.5%. As for
stellar ages, we quantify systematics of the order of 10-14% at most, but there are also very promising cases for which deviations remain within 4% depending on the
stars and constraints considered.
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All authors Saniya Khan, Gaël Buldgen, Jérôme Bétrisey, Rafael A. García, Savita Mathur
Quantum Physics
Parallel and Distributed Fermionic Simulation via Dynamic Encoding
Michael Williams de la Bastida and Peter V. Coveney
We demonstrate a simple and efficient method to parallelize and distribute Trotterized
Hamiltonian simulation of fermionic systems across multiple QPUs. Using combinatorial covering designs to define a minimal set of
fermion-
qubit encodings, we demonstrate communication cost scaling as $\mathcal{O}(M q^4 r)$ for a system of $M$ fermionic modes and Trotter number $r$, improving on the static encoding bound for $q$ QPUs, $\mathcal{O}(M^4 q r)$. We compare this approach to dynamic encoding using a randomised method, Pauli-weight based optimisation and hypergraph partitioning. Applying these to the
Hamiltonians of a range of molecular systems split across two QPUs, we find the combinatorial covering approach results in the lowest communication cost in all but the sparsest
Hamiltonians.
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Mesoscale and Nanoscale Physics
Rydberg excitons in core-shell nanostructures II. Plasmon-exciton interaction and enhancement
David Ziemkiewicz, Gerard Czajkowski and Sylwia Zielińska-Raczyńska
Interaction between Rydberg
excitons in core-shell Cu$_2$O nanostructures and surface plasmons is investigated. An enhancement of a quadrupole transitions to the Rydberg
exciton states in copper
oxide plasmonic nanaostructures is examined. A possibility of a modification of plasmonic enhancment (i.e., an average amplification factor) of electric field distributions in the vicinity of nanostructures, which depends on its shape and geometrical size, is also discussed.
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High Energy Physics (Phenomenology)
An information bound for multiplicities in rapidity windows of the dipole cascade behind the entanglement entropy picture
Olasantan Ebenezer Adelaja, Alex Prygarin and Karam Shekh Yusuf
In Mueller's dipole cascade without transverse dimensions, with one counted particle for each dipole produced in a window, the multiplicities in three consecutive rapidity windows are Poisson counts of one Gamma-distributed source. We show that at fixed middle multiplicity the outer two share less information than the Gaussian value $-\tfrac12\ln(1-\rho^2)$ of their partial correlation, a value that second moments alone determine. For windows of one common width at a constant splitting rate this value never exceeds $\tfrac12\ln(4/3)$. The Gaussian value is not a bound on mutual information in general, and for a source of the same mean and variance with another law the information can exceed it. The law of the counts keeps its form under migration of particles across window edges and detection losses when both act on each particle independently of the others and of the source, and its factorial cumulants of second and third order test necessary conditions for it. In Monte Carlo simulations of the cascade with transverse dimensions at leading logarithmic accuracy and fixed coupling, the counts are not Poisson counts of one source, so the bound is a result of the model without them. In the model without transverse dimensions the law also fixes the normalized second factorial cumulant of one window at $1/k$, with $k$ the number of initial dipoles. The values of this cumulant formed from the mean and variance that H1 publishes for deep inelastic scattering lie far below the value one of a cascade from a single initial dipole with one counted particle for each dipole produced in a window. The quantity bounded is a classical conditional mutual information between counted multiplicities.
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Chemical Physics
HOMO-LUMO Intervals from Modern Density Functionals as Fundamental Gap Estimators
H. Francisco, Javier Carmona-Espíndola, A. C. Cancio et al. (+2 more)
Use of the Kohn-Sham
eigenvalue gap (highest occupied molecular orbital to lowest unoccupied, HOMO-LUMO) as a fundamental gap (I-A, I= ionization potential, A= electron affinity)
estimator is a long-standing challenge for relatively simple exchange-correlation functionals, e.g. meta-GGAs. The LAK meta-GGA [T. Lebeda et al. Phys. Rev. Lett. 133, 136402 (2024)] was developed to emphasize certain constraints in ways intended to make the LAK KS gaps close to the HSE06 hybrid functional [A.V. Krudau et al. J.Chem. Phys. 125, 224106 (2006)] gaps. The LAK functional was tested against a small atomization data set and a very small bond length set, with no molecular HOMO-LUMO gap testing. Here we test LAK against widely used, large reference data sets for molecular heats of formation, bond lengths, harmonic frequencies, I, and A and compare with r2SCAN [J.W. Furness et al., J. Phys. Chem. Lett. 11, 8208 (2020)] as well as HSE06 and PBE0, a quite different hybrid. On these tests LAK does not give meaningfully better geometries, heats of formation, HOMO-LUMO gaps, or DFT IP
theorem satisfaction than r2SCAN. Compared against experimental I and A values the same holds; LAK results resemble r2SCAN results, not HSE06. Moreover, the HOMO and LUMO shifts generated by the NCAPR GGA [J. Carmona-Espindola et al., J. Chem. Phys. 157, 114109 (2022)] as derivative discontinuity estimates, correct the bare NCAPR HOMO and LUMO
eigenvalues to substantially better agreement with experiment for both fundamental gap and IP
theorem than do the meta-GGAs (LAK, r2SCAN) or hybrids (HSE, PBE0). We discuss possible reasons why LAK behaves differently for molecules and solids.
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All authors H. Francisco, Javier Carmona-Espíndola, A. C. Cancio, José Luis Gázquez, S. B. Trickey
Materials Science
Crystallographic-orientation dependence of the early-stage oxidation of Zr single crystals: an XPS study of suboxide formation and in-depth distribution
Joaquin Sacanell and Flavio Conde
The influence of crystallographic orientation on the early stages of the oxidation of pure Zr single
crystals was studied by X ray photoelectron spectroscopy (XPS). Two samples, cut from the same a-Zr single
crystal, were oxidized simultaneously at room temperature and O2 pressures of 1 X 10-8, 1 X 10-7 and 1 X 10-6 torr: one with its surface normal parallel to the c-axis (Z1, basal (0001) plane) and the other with its normal 12deg from that of a prismatic plane (Z2, near-prismatic orientation). At all three pressures the oxidation kinetics of both samples followed a three stage, logarithmic type behaviour, but the near prismatic sample (Z2) incorporated oxygen faster and to a greater extent than the basal sample (Z1) in every case. Deconvolution of the Zr 3d core level spectra resolved, in addition to metallic Zr and ZrO2, two sub-stoichiometric Zr O compounds, denoted (ZrO)a and (ZrO)b, with binding-energy shifts of 1.3 and 2.3 eV with respect to metallic Zr, consistent with sub
oxides previously reported for polycrystalline Zr. Angle resolved XPS showed that ZrO2 is the outermost compound in both orientations, while the two sub-
oxides are distributed nearly homogeneously through the film.
Oxide thicknesses, calculated from the attenuation of the metallic Zr 3d signal, ranged from 10 to 13 A for Z1 and from 14 to 19 A for Z2 depending on the oxidation pressure, in close agreement with earlier measurements on cold worked polycrystalline Zr, whose surface texture is dominated by prismatic-oriented grains.
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High Energy Physics (Phenomenology)
High-frequency gravitational waves from microscopic particle-graviton associated production in bubble collisions
Peilin Chen, Dayun Qiu, Zihong Cheng et al. (+1 more)
Cosmological first-order phase transitions are well-known sources of gravitational waves from bubble collisions and
plasma dynamics. In this work, we investigate an additional microscopic source directly arising from the associated production of particles and gravitons during bubble collisions. Focusing on runaway bubble walls, we calculate the gravitational wave spectra from two-body scalar-graviton production and three-body processes involving scalar or
fermion pairs accompanied by a graviton. We derive analytic approximations and numerically evaluate the resulting spectra, revealing a high-frequency gravitational wave component that can complement conventional lower-frequency signals from the same phase transition. This mechanism offers a potential multiband signature and establishes a connection between gravitational radiation and the production of dark matter or other new particles. Our findings provide a new physics target for future high-frequency gravitational wave experiments and a complementary probe of particle production in the early Universe.
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All authors Peilin Chen, Dayun Qiu, Zihong Cheng, Fa Peng Huang
Quantum Physics
Connes Distance in Discrete-Time Quantum Walks
Rayan Trabelsi, A. F. Reyes-Lega and Pablo Arrighi
We study the
geometric spread of discrete-time
quantum walks using Connes' distance formula. We introduce its discrete analogue by adapting the continuous spectral metric to the
lattice, with the Dirac operator replaced by the
unitary step operator. Focusing first on a (2+1)-dimensional
quantum walk, we evaluate the dynamical spread of localized wavepackets to compare propagation in free space against that under a uniform
magnetic field. We find that while the free walk shows linear ballistic growth, gauge-induced phases in the
magnetic walk constrain the admissible test operators, suppressing the long-time
geometric expansion. Furthermore, we apply this discrete framework to a (1+1)-dimensional plastic
quantum walk simulating an inhomogeneous spatial metric. The results demonstrate that the discrete Connes distance naturally captures the underlying spatially varying metric, providing a robust measure of the wavepacket's spread that adapts directly to the local simulated geometry.
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Quantum Physics · Cross-listed from cs.IT
COFI-DQI: Curve-based Optimal Function Intersection via Decoded Quantum Interferometry
Gretchen L. Matthews and Julia Shapiro
In 2025, Jordan et al. introduced Decoded
Quantum Interferometry (DQI), a
quantum algorithm for combinatorial optimization based on decoding. They considered Reed-Solomon decoding and its associated optimization problem, called Optimal
Polynomial Intersection (OPI), which may be viewed as a
polynomial regression problem over a finite field. DQI exhibits provable speedups on certain problem instances and establishes a connection between decoding problems and optimization tasks. Leveraging the well-understood dual structure and decoding theory of algebraic geometry codes from other curve families, we introduce COFI: Curve-based Optimal Function Intersection. By considering two-point Hermitian codes, Suzuki codes, and extended norm-trace codes, we broaden the range of algebraic geometry codes used in DQI and identify families that offer further improvements over one-point Hermitian codes in the Hermitian Optimal
Polynomial Intersection framework considered by Jordan and Gu. Depending on the family and parameter regime, these curves can reduce
quantum resource requirements or increase the number of constraints that can be considered.
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Chemical Physics
Scaling Density Functional Theory with Gaussian Splatting
Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan et al. (+3 more)
Density functional theory (DFT) strikes a practical balance between accuracy and computational cost in many problems of computational chemistry and materials science. However, many DFT calculations are limited by fixed atom-centered basis sets, which dictate how accuracy and cost scale with system size. We propose Gaussian Splatting for Density Functional Theory (GS-DFT), which represents molecular orbitals as a cloud of Gaussians whose positions, shapes, and mixing coefficients are optimized jointly by gradient descent to minimize the energy without training data. Conceptually, GS-DFT is 3D Gaussian splatting with the renderer replaced by
quantum mechanics. We introduce two key solver components: adaptive density fitting with screening for efficient evaluation of two-electron integrals, and a regularized differentiable orthogonalization of the molecular orbitals. Empirically, the optimized basis reaches the accuracy of the largest conventional basis sets with a fraction of the parameters, converging systematically in energy, density, and
nuclear forces. At equal parameter count, it captures the stretched-bond and anion physics that fixed bases only recover with specialized basis augmentation. The resulting solver exhibits quadratic peak
memory scaling in the cloud size, allowing us to simulate systems of up to 2,742 atoms (10,406 electrons) without any modifications at triple-
zeta scale using a single four-GPU node.
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All authors Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan, Marta Skreta, Kirill Neklyudov, Matija Medvidović
Mathematical Physics
Rotationally Symmetric Zoll Metrics with a Cubic Integral
Holger R. Dullin, Vladimir S. Matveev, Gleb P. Palshin et al. (+1 more)
We introduce a new method for constructing Zoll metrics that admit first integrals
polynomial in the momenta. The method uses Funk's form of the metric together with an algebraic relation between the first integrals. This reduces the problem to an algebraic system from which all unknown functions can be determined explicitly. In the case of a non-trivial cubic integral, we present an explicit two-parameter family of metrics that covers all such rotationally symmetric Zoll metrics on the $2$-sphere: every such metric is isometric to a member of this family. We compare these metrics with the earlier results of Valent, Duval, and Shevchishin.
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All authors Holger R. Dullin, Vladimir S. Matveev, Gleb P. Palshin, Serena Scapucci
Materials Science
Ferroelectric Switching in ZnO/Zn1-xMgxO Heterostructures: Atomistic Insights into Interfacial Coupling and Layer Architecture
Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay et al. (+4 more)
Ferroelectric switching in
heterostructures couples composition, layer
topology, temperature, and interfacial boundary conditions. ReaxFF molecular dynamics isolates these variables in ZnO/ Zn1- xMgxO/ZnO and Zn1-xMgxO/ZnO/ Zn1-xMgxO stacks. Within pristine, initially single-domain models, coupling to switchable Zn1-xMgxO reduces the applied field required to reverse ZnO by up to fivefold. Temperature generally lowers the coercive field, whereas Mg concentration produces a nonmonotonic response. At equal ZnO and Zn1-xMgxO (ZMO) proportions, structures with ZnO at the center switch at lower fields than those with ZMO at the center at all four temperatures examined, demonstrating a
topology-dependent response. Layer-resolved trajectories reveal
topology-dependent switching sequences with direction-dependent redistribution of normal stress near the heterointerfaces, consistent with a stress-assisted cooperative pathway. Limiting MgO-containing structures exhibit sequential multilevel switching or low-polarity trapping, depending on thickness and temperature. Fixed-charge atomistic simulations complement previous continuum descriptions by resolving structural, energetic, and local stress
evolution under a common applied field. TEM and STEM-EDS observations provide experimental structural context for the modeled architectures. Together, the results establish layer
topology and interfacial mechanical confinement as design variables for wurtzite ferroelectric
heterostructures.
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All authors Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay, Elizabeth C. Dickey, Jon-Paul Maria, Susan Trolier-McKinstry, Adri C.T. van Duin
Fluid Dynamics
A parallel solver for vortex-induced vibrations at zero mass ratio
Arthur Bawin, Joan Le Pouhaër, Stéphane Étienne et al. (+1 more)
We present a parallel strategy for the study of the
vortex-induced vibrations (VIV) of a rigid, massless cylinder mounted on translational springs, in two and three dimensions. Without mass or damping, its motion is governed solely by the fluid forces and the spring restoring force, and is an immediate response to the flow. We focus on low spring stiffness, yielding high reduced velocity and maximal oscillation amplitude. A monolithic finite element method in an arbitrary Lagrangian-Eulerian framework with implicit time stepping is proposed, solving the fluid flow, cylinder dynamics, and mesh motion simultaneously. Mesh movement is modelled with a linear elastic pseudo-solid with variable Lamé coefficients, and the no-slip condition on the cylinder is enforced with a Lagrange multiplier coupled to the position degrees of freedom; three strategies are explored to enforce this force-position coupling in a distributed framework. To the best of our knowledge, this work is the first to propose a distributed solver for three-dimensional fluid-structure interaction at zero mass ratio. The solver is verified with manufactured solutions, and exhibits second-order accuracy in time. A numerical study of two- and three-dimensional VIV for Reynolds numbers from 100 to 300 reproduces the VIV responses obtained in previous two-dimensional studies, and predicts nonperiodic 3D oscillations starting at $Re = 300$. Using the direct solver MUMPS, the proposed method scales to up to 768 compute cores.
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All authors Arthur Bawin, Joan Le Pouhaër, Stéphane Étienne, Cédric Béguin
Optics
Direct Observation of Switching-Wave Dynamics in 20 GHz Normal Dispersion Spiral Microresonators
Van Doan Le, Julien Fatome and Erwan Lucas
Integrated Kerr frequency combs are powerful tools for microwave photonics, spectroscopy, and optical communications. While traditional architectures rely on the anomalous-dispersion regime, this typically requires thick, highly strained silicon nitride layers that complicate standard CMOS-foundry fabrication. Thinner layers circumvent these fabrication constraints but yield normal-dispersion microcombs that generally require specific trigger mechanisms, such as deterministic seeding, due to the absence of spontaneous modulational instability. Here, we demonstrate the generation of a 20 GHz microcomb in the normal-dispersion regime, driven by a synchronized dual-pump scheme via electro-optic sidebands modulation. The platform leverages an Archimedean spiral geometry on a foundry-compatible, 350 nm-thin SiN platform. By employing adiabatic
curvature engineering, the resonator balances a compact footprint with an intrinsic quality factor exceeding $7 \times 10^6$, while effectively eliminating avoided mode crossings with higher order modes. This strong-dispersion architecture yields a low-repetition-rate microcomb featuring high power-per-line and picosecond-scale temporal profile, which enables the direct optical sampling and characterization of the out-coupled switching wave waveforms. The measured dynamics across a range of pump desynchronizations demonstrate excellent agreement with simulations. Our work establishes a scalable, strategy for footprint-efficient normal-dispersion microcomb generation at microwave frequencies, with potential for scaling to other wavelength ranges.
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Quantum Gases
Spatiotemporal Non-Hermitian Skin Effect with Floquet-Engineered Ultracold Atoms
Weijie Liang, Weiping Zhang and Keye Zhang
Non-Hermitian skin effect, the accumulation of bulk eigenstates at edges under open boundary conditions, has been observed across classical,
quantum, and synthetic platforms. Whether it can be generalized to the genuine time dimension remains open. We propose a spatiotemporal NHSE in the Floquet phase space via Floquet engineering of a ring-trapped ultracold atomic gas. Placing spatial and temporal degrees of freedom on an equal footing, we show that a single parent skin effect projects onto either domain. The spatial projection yields an NHSE with arbitrarily tunable skin locations, eliminating the need for physical open boundaries. The temporal projection gives time-domain nonreciprocity and periodic temporal funneling, consistent with causality. This establishes a unified spatiotemporal paradigm for NHSE and opens a route to non-Hermitian topological physics in time.
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Quantum Physics
A Three-Party W-State Quantum Secret Sharing Protocol with X-Gate Encoding and Forbidden-Outcome Detection
Timur R. Teregulov and Elena R. Loubenets
We develop a new three-party
quantum secret-sharing (QSS) protocol based on a three-
qubit W state. This protocol encodes the secret-sequence bits using X gates and employs randomly selected Hadamard operations and measurement bases to generate information and security-test rounds. We evaluate the efficiency of the proposed protocol and analyze its security against an internal adversary performing intercept-and-resend and entangle-and-measure attacks, deriving the corresponding detection probabilities. The analysis of the entangle-and-measure attack shows that extracting information through an ancillary system leads to a nonzero probability of forbidden outcomes in the test rounds, thereby enabling the detection of the attack. The proposed protocol is implemented in Python using the Qsikit framework and executed on
quantum processors. Its performance is evaluated in terms of the
quantum bit error rate (QBER) for information rounds under different secret-bit encoding configurations. The experimental results demonstrate that the QBER depends noticeably on the
quantum processor used.
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